But McCain got 51.75% of the vote in Nueces county. Nueces county was actually the most populous county in Texas that voted for McCain.
Unless I misunderstand you, you are incorrect. Off the top of my head I suggest Tarrant, Collin, Ft Bend, and Denton, are all bigger and voted for McCain. Williamson and Galveston have as many or more voters though their pop may be less.